* [PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__
2012-08-23 18:15 [PATCH 0/4] [GIT PULL] ftrace: Use of __fentry__ Steven Rostedt
@ 2012-08-23 18:15 ` Steven Rostedt
2012-08-23 18:47 ` Andi Kleen
2012-08-23 18:15 ` [PATCH 2/4] ftrace: Add -mfentry to Makefile on function tracer Steven Rostedt
` (2 subsequent siblings)
3 siblings, 1 reply; 6+ messages in thread
From: Steven Rostedt @ 2012-08-23 18:15 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Masami Hiramatsu, Frederic Weisbecker,
Thomas Gleixner, H. Peter Anvin, H. Peter Anvin, John Reiser,
Ingo Molnar, Andi Kleen
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With gcc 4.6.0 the -mfentry feature places the function profiling
call at the start of the function. When this is used, the call is
to __fentry__ and not mcount.
Change recordmcount.c to record both callers to __fentry__ and
mcount.
Link: http://lkml.kernel.org/r/20120807194058.990674363@goodmis.org
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: John Reiser <jreiser@bitwagon.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
scripts/recordmcount.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h
index 54e35c1..9d1421e 100644
--- a/scripts/recordmcount.h
+++ b/scripts/recordmcount.h
@@ -261,11 +261,13 @@ static unsigned get_mcountsym(Elf_Sym const *const sym0,
&sym0[Elf_r_sym(relp)];
char const *symname = &str0[w(symp->st_name)];
char const *mcount = gpfx == '_' ? "_mcount" : "mcount";
+ char const *fentry = "__fentry__";
if (symname[0] == '.')
++symname; /* ppc64 hack */
if (strcmp(mcount, symname) == 0 ||
- (altmcount && strcmp(altmcount, symname) == 0))
+ (altmcount && strcmp(altmcount, symname) == 0) ||
+ (strcmp(fentry, symname) == 0))
mcountsym = Elf_r_sym(relp);
return mcountsym;
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__
2012-08-23 18:15 ` [PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
@ 2012-08-23 18:47 ` Andi Kleen
0 siblings, 0 replies; 6+ messages in thread
From: Andi Kleen @ 2012-08-23 18:47 UTC (permalink / raw)
To: Steven Rostedt
Cc: linux-kernel, Ingo Molnar, Andrew Morton, Masami Hiramatsu,
Frederic Weisbecker, Thomas Gleixner, H. Peter Anvin,
H. Peter Anvin, John Reiser, Ingo Molnar, Andi Kleen
I did a quick read of the patches and they all look good to me.
Acked-by: Andi Kleen <ak@linux.intel.com>
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 2/4] ftrace: Add -mfentry to Makefile on function tracer
2012-08-23 18:15 [PATCH 0/4] [GIT PULL] ftrace: Use of __fentry__ Steven Rostedt
2012-08-23 18:15 ` [PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
@ 2012-08-23 18:15 ` Steven Rostedt
2012-08-23 18:15 ` [PATCH 3/4] ftrace: Do not test frame pointers if -mfentry is used Steven Rostedt
2012-08-23 18:15 ` [PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64 Steven Rostedt
3 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2012-08-23 18:15 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Masami Hiramatsu, Frederic Weisbecker,
Thomas Gleixner, H. Peter Anvin, H. Peter Anvin, Ingo Molnar,
Michal Marek, Andi Kleen
[-- Attachment #1: Type: text/plain, Size: 2029 bytes --]
Thanks to Andi Kleen, gcc 4.6.0 now supports -mfentry for x86
(and hopefully soon for other archs). What this does is to have
the function profiler start at the beginning of the function
instead of after the stack is set up. As plain -pg (mcount) is
called after the stack is set up, and in some cases can have issues
with the function graph tracer. It also requires frame pointers to
be enabled.
The -mfentry now calls __fentry__ at the beginning of the function.
This allows for compiling without frame pointers and even has the
ability to access parameters if needed.
If the architecture and the compiler both support -mfentry then
use that instead.
Link: http://lkml.kernel.org/r/20120807194059.392617243@goodmis.org
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
Makefile | 6 +++++-
kernel/trace/Kconfig | 5 +++++
2 files changed, 10 insertions(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index ddf5be9..e7ca93f 100644
--- a/Makefile
+++ b/Makefile
@@ -609,7 +609,11 @@ KBUILD_CFLAGS += $(call cc-option, -femit-struct-debug-baseonly)
endif
ifdef CONFIG_FUNCTION_TRACER
-KBUILD_CFLAGS += -pg
+ifdef CONFIG_HAVE_FENTRY
+CC_USING_FENTRY := $(call cc-option, -mfentry -DCC_USING_FENTRY)
+endif
+KBUILD_CFLAGS += -pg $(CC_USING_FENTRY)
+KBUILD_AFLAGS += $(CC_USING_FENTRY)
ifdef CONFIG_DYNAMIC_FTRACE
ifdef CONFIG_HAVE_C_RECORDMCOUNT
BUILD_C_RECORDMCOUNT := y
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 8c4c070..9301a0e 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -49,6 +49,11 @@ config HAVE_SYSCALL_TRACEPOINTS
help
See Documentation/trace/ftrace-design.txt
+config HAVE_FENTRY
+ bool
+ help
+ Arch supports the gcc options -pg with -mfentry
+
config HAVE_C_RECORDMCOUNT
bool
help
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 3/4] ftrace: Do not test frame pointers if -mfentry is used
2012-08-23 18:15 [PATCH 0/4] [GIT PULL] ftrace: Use of __fentry__ Steven Rostedt
2012-08-23 18:15 ` [PATCH 1/4] ftrace: Make recordmcount.c handle __fentry__ Steven Rostedt
2012-08-23 18:15 ` [PATCH 2/4] ftrace: Add -mfentry to Makefile on function tracer Steven Rostedt
@ 2012-08-23 18:15 ` Steven Rostedt
2012-08-23 18:15 ` [PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64 Steven Rostedt
3 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2012-08-23 18:15 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Masami Hiramatsu, Frederic Weisbecker,
Thomas Gleixner, H. Peter Anvin, H. Peter Anvin, Ingo Molnar,
Andi Kleen
[-- Attachment #1: Type: text/plain, Size: 1626 bytes --]
The function graph has a test to check if the frame pointer is
corrupted, which can happen with various options of gcc with mcount.
But this is not an issue with -mfentry as -mfentry does not need nor use
frame pointers for function graph tracing.
Link: http://lkml.kernel.org/r/20120807194059.773895870@goodmis.org
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace_functions_graph.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace_functions_graph.c b/kernel/trace/trace_functions_graph.c
index ce27c8b..99b4378 100644
--- a/kernel/trace/trace_functions_graph.c
+++ b/kernel/trace/trace_functions_graph.c
@@ -143,7 +143,7 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
return;
}
-#ifdef CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST
+#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
/*
* The arch may choose to record the frame pointer used
* and check it here to make sure that it is what we expect it
@@ -154,6 +154,9 @@ ftrace_pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret,
*
* Currently, x86_32 with optimize for size (-Os) makes the latest
* gcc do the above.
+ *
+ * Note, -mfentry does not use frame pointers, and this test
+ * is not needed if CC_USING_FENTRY is set.
*/
if (unlikely(current->ret_stack[index].fp != frame_pointer)) {
ftrace_graph_stop();
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 4/4] ftrace/x86: Add support for -mfentry to x86_64
2012-08-23 18:15 [PATCH 0/4] [GIT PULL] ftrace: Use of __fentry__ Steven Rostedt
` (2 preceding siblings ...)
2012-08-23 18:15 ` [PATCH 3/4] ftrace: Do not test frame pointers if -mfentry is used Steven Rostedt
@ 2012-08-23 18:15 ` Steven Rostedt
3 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2012-08-23 18:15 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Masami Hiramatsu, Frederic Weisbecker,
Thomas Gleixner, H. Peter Anvin, Ingo Molnar, Andi Kleen
[-- Attachment #1: Type: text/plain, Size: 5552 bytes --]
If the kernel is compiled with gcc 4.6.0 which supports -mfentry,
then use that instead of mcount.
With mcount, frame pointers are forced with the -pg option and we
get something like:
<can_vma_merge_before>:
55 push %rbp
48 89 e5 mov %rsp,%rbp
53 push %rbx
41 51 push %r9
e8 fe 6a 39 00 callq ffffffff81483d00 <mcount>
31 c0 xor %eax,%eax
48 89 fb mov %rdi,%rbx
48 89 d7 mov %rdx,%rdi
48 33 73 30 xor 0x30(%rbx),%rsi
48 f7 c6 ff ff ff f7 test $0xfffffffff7ffffff,%rsi
With -mfentry, frame pointers are no longer forced and the call looks
like this:
<can_vma_merge_before>:
e8 33 af 37 00 callq ffffffff81461b40 <__fentry__>
53 push %rbx
48 89 fb mov %rdi,%rbx
31 c0 xor %eax,%eax
48 89 d7 mov %rdx,%rdi
41 51 push %r9
48 33 73 30 xor 0x30(%rbx),%rsi
48 f7 c6 ff ff ff f7 test $0xfffffffff7ffffff,%rsi
This adds the ftrace hook at the beginning of the function before a
frame is set up, and allows the function callbacks to be able to access
parameters. As kprobes now can use function tracing (at least on x86)
this speeds up the kprobe hooks that are at the beginning of the
function.
Link: http://lkml.kernel.org/r/20120807194100.130477900@goodmis.org
Acked-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Andi Kleen <andi@firstfloor.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
arch/x86/Kconfig | 1 +
arch/x86/include/asm/ftrace.h | 7 ++++++-
arch/x86/kernel/entry_64.S | 32 +++++++++++++++++++++++++++-----
arch/x86/kernel/x8664_ksyms_64.c | 6 +++++-
4 files changed, 39 insertions(+), 7 deletions(-)
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a2d19ee..28dd891 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -36,6 +36,7 @@ config X86
select HAVE_KRETPROBES
select HAVE_OPTPROBES
select HAVE_FTRACE_MCOUNT_RECORD
+ select HAVE_FENTRY if X86_64
select HAVE_C_RECORDMCOUNT
select HAVE_DYNAMIC_FTRACE
select HAVE_FUNCTION_TRACER
diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
index a6cae0c..9a25b52 100644
--- a/arch/x86/include/asm/ftrace.h
+++ b/arch/x86/include/asm/ftrace.h
@@ -35,7 +35,11 @@
#endif
#ifdef CONFIG_FUNCTION_TRACER
-#define MCOUNT_ADDR ((long)(mcount))
+#ifdef CC_USING_FENTRY
+# define MCOUNT_ADDR ((long)(__fentry__))
+#else
+# define MCOUNT_ADDR ((long)(mcount))
+#endif
#define MCOUNT_INSN_SIZE 5 /* sizeof mcount call */
#ifdef CONFIG_DYNAMIC_FTRACE
@@ -46,6 +50,7 @@
#ifndef __ASSEMBLY__
extern void mcount(void);
extern atomic_t modifying_ftrace_code;
+extern void __fentry__(void);
static inline unsigned long ftrace_call_adjust(unsigned long addr)
{
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index b7a81dc..ed767b7 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -68,10 +68,18 @@
.section .entry.text, "ax"
#ifdef CONFIG_FUNCTION_TRACER
+
+#ifdef CC_USING_FENTRY
+# define function_hook __fentry__
+#else
+# define function_hook mcount
+#endif
+
#ifdef CONFIG_DYNAMIC_FTRACE
-ENTRY(mcount)
+
+ENTRY(function_hook)
retq
-END(mcount)
+END(function_hook)
/* skip is set if stack has been adjusted */
.macro ftrace_caller_setup skip=0
@@ -84,7 +92,11 @@ END(mcount)
movq RIP(%rsp), %rdi
subq $MCOUNT_INSN_SIZE, %rdi
/* Load the parent_ip into the second parameter */
+#ifdef CC_USING_FENTRY
+ movq SS+16(%rsp), %rsi
+#else
movq 8(%rbp), %rsi
+#endif
.endm
ENTRY(ftrace_caller)
@@ -177,7 +189,8 @@ END(ftrace_regs_caller)
#else /* ! CONFIG_DYNAMIC_FTRACE */
-ENTRY(mcount)
+
+ENTRY(function_hook)
cmpl $0, function_trace_stop
jne ftrace_stub
@@ -199,7 +212,11 @@ trace:
MCOUNT_SAVE_FRAME
movq RIP(%rsp), %rdi
+#ifdef CC_USING_FENTRY
+ movq SS+16(%rsp), %rsi
+#else
movq 8(%rbp), %rsi
+#endif
subq $MCOUNT_INSN_SIZE, %rdi
call *ftrace_trace_function
@@ -207,7 +224,7 @@ trace:
MCOUNT_RESTORE_FRAME
jmp ftrace_stub
-END(mcount)
+END(function_hook)
#endif /* CONFIG_DYNAMIC_FTRACE */
#endif /* CONFIG_FUNCTION_TRACER */
@@ -215,9 +232,14 @@ END(mcount)
ENTRY(ftrace_graph_caller)
MCOUNT_SAVE_FRAME
+#ifdef CC_USING_FENTRY
+ leaq SS+16(%rsp), %rdi
+ movq $0, %rdx /* No framepointers needed */
+#else
leaq 8(%rbp), %rdi
- movq RIP(%rsp), %rsi
movq (%rbp), %rdx
+#endif
+ movq RIP(%rsp), %rsi
subq $MCOUNT_INSN_SIZE, %rsi
call prepare_ftrace_return
diff --git a/arch/x86/kernel/x8664_ksyms_64.c b/arch/x86/kernel/x8664_ksyms_64.c
index 6020f6f..1330dd1 100644
--- a/arch/x86/kernel/x8664_ksyms_64.c
+++ b/arch/x86/kernel/x8664_ksyms_64.c
@@ -13,9 +13,13 @@
#include <asm/ftrace.h>
#ifdef CONFIG_FUNCTION_TRACER
-/* mcount is defined in assembly */
+/* mcount and __fentry__ are defined in assembly */
+#ifdef CC_USING_FENTRY
+EXPORT_SYMBOL(__fentry__);
+#else
EXPORT_SYMBOL(mcount);
#endif
+#endif
EXPORT_SYMBOL(__get_user_1);
EXPORT_SYMBOL(__get_user_2);
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread